Cork Institute of Technology
Bachelor of Engineering (Honours) in Electronic Engineering – Award
(NFQ Level – 8)
Summer 2006
APPLIED DIGITAL SIGNAL PROCESSING
(Time: 2 Hours)
Answer any four questions
[each 25 marks]
Maximum available mark is 100.
Examiners: Dr. Joseph Connell
Prof. Gerard Hurley
Dr. Sean Foley
Q1. (a) A dual tone signal comprising a unity-amplitude, 10Hz sine wave and a unity-
amplitude, 12Hz sine wave is sampled at 100Hz. Discuss the process of using
the samples thus produced to spectrally analyse the signal accurately. [10 marks]
(b) A 16Hz, unity amplitude sinewave is sampled at 80Hz. Using a Goertzel cell
and one period of samples, evaluate the DFT for the signal in at the frequency
of interest. [15 marks]
Q2. (a) Spectral analysis of a noisy signal is required using the Welch Method. N
samples are available. Discuss the strategy involved and comment on its
performance in comparison to a straight DFT on the N samples. [10 marks]
(b) The causal impulse response of an LTI system is given as
=
)(nh {-3 1 4}.
The causal input is given as
=
)(nx {2 -1}. Show that )(*)()( lhlrlr xxxy −
=
. [15 marks]
Q3. (a) File1 contains digital data sampled at s
f Hz. Describe in detail using
amplitude plots the spectral implications of creating a new file2 by inserting 2
zeros between every sample in file1.
Hence, given a file of data sampled at s
f, outline a strategy for creating a new
file of data consistent with the original signal being sampled at s
If where I is
an integer. [15 marks]
(b) A signal is sampled at 8kHz. It is required to generate a second sequence of
samples corresponding to a sampling frequency 24kHz. Write efficient
software to perform the task. Assume any filter used is 4th order. [10 marks]
